In fuel delivery systems for internal combustion engines, particularly two-stroke engines, it has heretofore been proposed to provide a diaphragm pump responsive to pressure pulsations from the engine crankcase for feeding fuel from a supply or tank to engine fuel injectors or the like. Fuel pressures obtainable with systems of this type are typically on the order of 10 to 11 psi. A general object of the present invention is to provide a fuel delivery system that is adapted to achieve fuel delivery pressures on the order of 25 to 30 psi or more, that obtains pumping energy from reciprocation of the engine without electronic control circuitry or energy input, that is economical to manufacture, and that provides reliable operation over an extended lifetime.
A fuel pump in accordance with one aspect of the present invention comprises a chamber having an inlet for coupling to a fuel source and an outlet for delivering fuel under pressure to engine fuel injectors or the like. A pump mechanism is disposed in the chamber and coupled to first magnetic material for reciprocating the mechanism within the chamber, and thereby pumping fuel from the inlet to the outlet. Second magnetic material is mounted for motion adjacent to the first magnetic material in synchronism with operation of the engine, such that magnetic forces imparted in the first magnetic material as the second magnetic material moves therepast reciprocates the pump mechanism within the chamber. In the preferred embodiment of the invention, the pump mechanism comprises a diaphragm that spans the pumping chamber, and the first magnetic material comprises a piston coupled to the diaphragm by a rod. The second magnetic material comprises a permanent magnet mounted on the periphery of the flywheel of the engine for rotation past the magnetic piston to reciprocate the diaphragm within the chamber.
In accordance with another aspect of the present invention, a two-stage fuel delivery system for an internal combustion engine includes a first stage pump having a first pump chamber with an inlet coupled to a fuel source, an outlet and a diaphragm responsive to pressure pulsations from the engine crankcase for reciprocation within the chamber. A second stage pump includes a second pump chamber having an inlet coupled to the outlet of the first chamber, an outlet for delivering fuel under pressure to engine fuel injectors or the like, a permanent magnet for mounting on the flywheel of the engine for rotation in synchronism with operation of the engine, and a diaphragm in the second chamber operatively coupled to the magnet for reciprocation with the second chamber responsive to rotation of the magnet to pump fuel from the inlet to the outlet of the second chamber. The two-stage pump achieves fuel delivery pressures on the order of 25 to 30 psi or more employing energy from reciprocation of the engine and without requiring control electronics or electrical energy input.